Electrostatic capacity-type sensor

• US 20090015270A1
• Filed: 06/03/2008
• Published: 01/15/2009
• Est. Priority Date: 07/12/2007
• Status: Active Grant

• Current Assignee: Sumitomo Riko Company Limited.
• Original Assignee: Tokai Rubber Industries Limited
• Inventors: Hashimoto, Kazunobu, Hayakawa, Tomonori
• Granted Patent: US 8,451,011 B2
• Time in Patent Office: Days
• US Class Current: 324/686
• CPC Class Codes: G01L 1/142 using capacitors

Abstract

An object of the present invention is to provide an electrostatic capacity-type sensor which is excellent in durability and can detect bending-deformation. An electrostatic capacity-type sensor comprises a dielectric film made of an elastomer and a pair of electrodes arranged via the dielectric film, and detects the deformation based on a change in the electrostatic capacity between the pair of electrodes. The pair of electrodes have an elastomer and a conductive filler blended in said elastomer, and are expansible/contractible depending on the deformation of the dielectric film, and exhibit a small change in the conductivity even when expanded and contracted.

Claims

1. An electrostatic capacity-type sensor comprising a dielectric film made of an elastomer and a pair of electrodes arranged via said dielectric film, wherein:

said pair of electrodes have an elastomer and a conductive filler blended in said elastomer, and are expansible/contractible depending on the deformation of said dielectric film, and exhibit a small change in the conductivity even when expanded and contracted; and

a deformation is detected based on a change in the electrostatic capacity between said pair of electrodes.

2. An electrostatic capacity-type sensor according to claim 1, wherein said pair of electrodes consist of an elastomer composition including said elastomer and said conductive filler;

and

in a percolation curve indicating a relationship between a blending amount of said conductive filler and an electric resistance of said elastomer composition, the blending amount (critical volume fraction;

φ

c) of said conductive filler at a first flexure point, at which electric resistance lowers to cause a transition between insulator and conductor, is 25 vol % or less.

3. An electrostatic capacity-type sensor according to claim 1, wherein said conductive filler is made of carbon material.

4. An electrostatic capacity-type sensor according to claim 1, wherein said elastomer as a material of said dielectric film includes one or more compounds selected from the group consisting of silicone rubber, acrylonitrile-butadien copolymer rubber, acrylic rubber, epichlorohydrin rubber, chlorosulfonated polyethylene, chlorinated polyethylene, and urethane rubber.

5. An electrostatic capacity-type sensor according to claim 1, wherein said elastomer as a material of said pair of electrodes includes one or more compounds selected from the group consisting of silicone rubber, ethylene-propylene copolymer rubber, natural rubber, styrene-butadien copolymer rubber, acrylonitrile-butadien copolymer rubber, acrylic rubber, epichlorohydrin rubber, chlorosulfonated polyethylene, chlorinated polyethylene, and urethane rubber.

6. An electrostatic capacity-type sensor according to claim 1, wherein a restraint member for restraining an elastic deformation of a surface of at least one of said pair of electrodes, which is elastically bending-deformable, is arranged on said surface.

7. An electrostatic capacity-type sensor according to claim 6, wherein said restraint member for restraining an elastic deformation of a surface of one of said pair of electrodes is arranged on said surface;

and

during bending-deformation, the direction of said bending-deformation can be discriminated based on a change in the electrostatic capacity between said pair of electrodes.

8. An electrostatic capacity-type sensor according to claim 1, wherein a pair of sensor elements including said dielectric film and said pair of electrodes are arranged on both respective sides of a plate-shaped, elastically bending-deformable reference member;

and

utilizing a fact that the increase/decrease of the film thickness of said dielectric film on both the sides of said reference member becomes reverse during bending-deformation, said bending-deformation is detected based on a difference between an electrostatic capacity change in one of said sensor elements and an electrostatic capacity change in the other of said sensor elements.

9. An electrostatic capacity-type sensor according to claim 8, wherein restraint members for restraining an elastic deformation of respective surfaces of said sensor elements are further arranged on said surfaces.